The auto-message module is now configurable (in SCFG->System->Loadable Modules)

defaults to "automsg" (e.g. automsg.js). So now shells that use the Baja
auto_message function (or call JS bbs.auto_msg()) will execute the module
configured here automatically.
Deleted the old-crufty sbbs_t::automsg() implementation. We have the work-alike
auto.js, but really it's time to totally overhaul that sucker into something
modernish (e.g. allow *editing* the message you wrote <gasp>).